There are situations where users want a data store in one place to be a copy of a data store in another place. In order to propagate changes made in one store to another, synchronization methods have been developed to propagate the changes between the different stores, so that the information in the different stores correlate to each other at discrete times, or checkpoints. Another method has changes being transferred discretely at the time of change by exchanging notifications. Some devices employ both methods of keeping their data store in synchronization, but encounter problems when notification delivery is delayed and said delayed notification arrives after a synchronization of that change has already been performed.
For example, some devices receive notifications that are not current with the current synchronization checkpoint between the devices. This may result in notifications being improperly processed.